Evolution Gun Works Recoil Spring ISMI 1911 Steel 16 lb. Not recommended for use with Commander Models without removing multiple coils.ISMI?s proprietary design features enhance the spring?s ability to hold the pistol in battery longer when fired to maximize energy dispersion and reduce sight movement. All ISMI Springs are made from silicone chrome instead of 150 year old music wire. Every ISMI spring is heat treated shot peened & stress relieved to enhance durability consistency and reliability. ISMI is a contractor of the U.S. government and produces springs used in machine guns with incredibly high cycling rates. Also the creator of ISMI springs obtained his knowledge from extensive research in the development of springs used in Indy car racing.A note from the manufacturer: Maximum Service Temperature of ISMI?s material goes up to 700F. Music wire has a maximum service temperature of 250F and can be negatively affected at temperatures as low as 175F. This is important because temperatures approaching or exceeding the maximum service temperature are highly detrimental to spring life. Exposure to maximum service temperatures promotes additional spring set and is detrimental to the relaxation of the spring. In other words the spring will not decompress as rapidly as it should. Available in 7 8 9 10 11 12 14 16 18 20lbs. Specifications for Evolution Gun Works Recoil Spring ISMI 1911: Manufacturer: Evolution Gun Works Color: Silver Finish: Stainless Fabric/Material: Steel Gun Make: 1911 Platform Gun Model: 1911 Condition: New Package Contents: Evolution Gun Works Recoil Spring ISMI 1911 What firearm models does the manufacturer say Evolution Gun Works Recoil Spring ISMI 1911 is compatible with? The manufacturer suggests that Evolution Gun Works Recoil Spring ISMI 1911 is compatible with 1911Evolution Gun Works 10616: Recoil Spring ISMI 1911 Steel 16 lb